Trucks such as pickup trucks and the like are often used to transport small cargo loads and/or to make deliveries and pickups. One of the difficulties of using such trucks is that of loading and unloading heavy or awkward cargo when a loading dock of proper height is not available. For example, the cargo box of a pickup truck can be three or more feet off of the ground, making it difficult to load or unload cargo to and from the cargo box.
Various attempts have been made in the past to make it easier to load and unload cargo. For example, Canadian patent application no. 2,145,259, published Sep. 23, 1995, illustrates a vehicle having a U-shaped chassis with a drop tray decking. The tray is powered by hydraulics at each corner of the decking to raise and lower the tray. However, such a system requires a sophisticated control system for activating the hydraulics to ensure that each of the hydraulic cylinders operate simultaneously.
U.S. Pat. Nos. 4,902,188 to Page and 5,288,197 to Harris show systems wherein the cargo platform of a vehicle and a trailer, respectively, is lowered by pivoting the platform rearward and downward to facilitate easier loading and unloading of cargo. These systems suffer from the fact that they require a clear space behind the vehicle or trailer to allow the cargo platform to move rearward as it is pivoted downward.
Vehicles according to U.S. Pat. No. 4,902,188 to Page were briefly offered for sale in the United States under the trademark KELPIE KARGO. However, such vehicles were not commercially successful.
On some vehicles, the antilock braking system sensors are mounted on the rear differential of the drivetrain. On removing the rear axle to convert such vehicles to have an elevating cargo box, it was discovered that the antilock braking system brakes would not function properly without the sensor. Further, certain manufacturers use the antilock braking system sensor as a digital input for the speedometer and without a sensor, the speedometer would not operate.